Transit from CDG to Gare De Lyon

After collecting your luggage, follow the signage and the painted footsteps on the floor to the official taxi line and take a taxi. The fare will be 56€, no need to tip. Do not pay attention to people asking if you need a taxi.
Scroll down to “Where are the taxi ranks at Paris-CDG Airport” at https://www.parisaeroport.fr/en/passengers/transport-parking/taxi/cdg for info on where the stands are for every terminal in case you miss or do not want to look for the signage.

If your French is workable, after saying Bonjour, follow up with your destination and away you go. If your French is not good, write the destination and the amount on a card and hand it to the driver after the greeting. Including the amount of the fare is not necessary but I suggest it so everyone involved knows that you know about the flat rate fare.

or take the RER-B train from the airport to Gare du Nord and change there to the RER-D for 2 further stops to Gare de Lyon. Make yourself pickpocket proof and relax.

Both the taxi and the RER will be crowded at 8 am or so with rush hour unless you will be arriving on Sunday.

It is a Sunday though. Google and Citymapper shows I take the RER to Chatelet and then to Gare De Lyon.

Or Gare du Nord as Nigel wrote. Look at your apps to see which one has the change on the same platform because I forget which direction has the cross-platform change. If it’s Châtelet Les Halles, do it there. Otherwise Gare du Nord if the hallways are close together.
Or take a taxi.

Where are you going from GdL? You may have train options directly from CDG, not requiring you to go in to Paris.

Les Halles is cross platform from the B to the A.